The present invention relates to gas flow units which are adapted to be mounted on gas administration machines. More particularly, the present invention relates to anaesthetic vaporisers which are adapted to be mounted on anaesthesia machines for the administration of gaseous anaesthetics or analgesics or other "medical" gases or gas mixtures, such as oxygen or air.
For the avoidance of doubt throughout this specification the term "anaesthetic" is intended to embrace gaseous anaesthetics, gaseous analgesics or other "medical" gases or gas mixtures such as oxygen or air.
Conventionally, anaesthesia machines frequently incorporate two or more separate anaesthetic vaporisers. Each vaporiser is arranged to dispense a specific amount of a particular anaesthetic, for example, halothane, enflurane, methoxyflurane etc., in a patient's breathing circuit or gas line.
In United Kingdom patent specification No. 1385670 there is described an anaesthesia machine on which one or more vaporisers can be mounted in a removable, plug-in fashion. A plug-in system of this nature simplifies the installation and removal of the vaporisers from the machine thereby facilitating maintenance and cleaning of the vaporisers as well as replacing a vaporiser should it fail during operation. Furthermore, this system is of great value to the anaesthetist in allowing him to change vaporisers both easily and quickly.
In United Kingdom patent specification No. 2052271, there is described an arrangement whereby two or more vaporisers are mounted on a back bar of an anaesthesia machine. Each vaporiser has an interlock system which includes at least one pin extendible outwardly from the vaporiser on manipulation of the control means for the vaporiser to its operating position to prevent the control means of a similar adjacent vaporiser mounted on the anaesthesia machine from being manipulated to its operating position.
However, if the vaporiser control means were to be subjected to misuse by the application of excessive force thereto it is possible that the interlock system could be overridden.
If this were to occur, it could mean that two or more vaporisers on the same anaesthesia machine could be operated at the same time thereby administering their respective anaesthetics to a patient.